This invention relates generally to electronic security systems, and more particularly, to methods and apparatus for implementing a security system having radio frequency identification (RFID) tags or infrared identification (IRID) tags, wherein the RFID or IRID tags have long life and low cost.
RFID tags are available in two basic versions, namely, “active” and “passive.” Passive RFID tags have no internal power supply. Instead, an incoming radio signal provides just enough power to activate a CMOS integrated circuit (IC) in the tag. When activated, an outbound backscatter signal is transmitted back to the reader. This transmitted response can include an ID number or code, as well as other data. Passive RFID tags are relatively inexpensive, but the distance at which they can be read is limited, and relatively expensive readers are required.
On the other hand, active RFID tags use their own internal power source to power ICs and to transmit the outgoing signal. Because of the presence of an internal power source, these tags can transmit with greater power and range than can passive RFID tags. Thus, active RFID tags can be more reliable than passive RFID tags and have larger memories. However, all these advantages accrue at the expense of the RFID tag having a lifetime limited by the lifetime of the internal power source, which is always being drained by the transmitter.
Some alarm systems suitable for installation in a dwelling or a light commercial building use relatively inexpensive passive RFID tags, but, as a result, require many relatively expensive active readers. The cost of multiple readers is multiplied by the number of readers installed. These readers are already relatively expensive and processor intensive, and the readers drain a considerable amount of current. As the current requirement increases with the number of readers, the current requirement for the entire system increases as does the size of needed backup batteries.
Some other alarm systems suitable for use in the same types of buildings use active RFID tags and active read stations. Known active tags used in security systems contain batteries and RF receivers/detectors that consume large amounts of current. Thus, the batteries contained therein last only one to three years, after which the RFID tags must be replaced.